1. Field of the Invention
The present invention relates to an image forming apparatus having a plurality of toner cartridges for containing toners for replenishment, an intermediate hopper to which the toner contained in the toner cartridge is to be supplied, and a developing device to which the toner supplied to the intermediate hopper is to be supplied.
2. Description of the Related Art
In general, an image forming apparatus that utilizes an electrophotography technique is composed of a photoreceptor which is a rotating image carrier, and a charging section, an exposure section, a developing section, a transfer section, a fixing section, a cleaning section, and a de-electrifying section that are arranged around the photoreceptor. The charging section applies electric charge uniformly over the surface of the photoreceptor. The exposure section exposes the surface of the photoreceptor in a charged state to light in accordance with image information to thereby form an electrostatic latent image. The developing section agitates a toner so that it can be electrically charged by friction, and then causes the frictionally-charged toner to adhere to the electrostatic latent image formed on the surface of the photoreceptor to thereby form a toner image. The transfer section transfers the toner image onto a recording medium by applying, to the recording medium, electric charge of a polarity reverse to the polarity of the charge borne on the toner. The fixing section fixes the transferred toner image onto the recording medium by means of application of heat, pressurization, or otherwise. The cleaning section collects toner portions that remain on the surface of the photoreceptor because of not having been transferred onto the recording medium. The de-electrifying section de-electrifies the photoreceptor following the completion of the transfer of the toner image. By virtue of the image forming apparatus employing the electrophotography technique thereby constructed, a desired image can be formed on the recording medium.
In such an image forming apparatus, since a toner for use in the developing section thereof to perform development is a consumable product, there is provided a toner replenishment section for effecting the replenishment of a supply of a toner on a developer housing which is a container for containing a toner to be provided for the developing section. In general, the toner replenishment section acts to replenish the developer housing with a toner contained in a toner cartridge designed so as to be attachable to and detachable from the image forming apparatus by way of an intermediate hopper.
In this construction, upon the toner contained in the toner cartridge running out due to toner replenishment for the developer housing, the operation of the image forming apparatus is brought to a halt. Then, the toner cartridge empty of the toner is replaced with a new toner cartridge to replenish the developer housing with a toner. By doing so, the image forming operation can be carried out once again.
In recent years, there have been developed electrophotographic image forming apparatuses such as copying machines and printers intended for general users that are used very frequently with consumption of a large amount of a toner. In such an apparatus, a plurality of toner cartridges can be mounted. Therefore, even if one of the toner cartridges is emptied, toner replenishment can be effected with another toner cartridge, and the toner cartridge empty of the toner can be replaced with the new one in the course of toner replenishment effected with use of another toner cartridge.
In a case of a color image forming apparatus for printing full-color images, toners of four colors: cyan; magenta; yellow; and black are used. In this case, even if only one toner cartridge is mounted for each of the colors on an individual basis, four toner cartridges will be necessary after all. It is thus difficult to mount a plurality of toner cartridges per color.
In regard to the replacement of the toner cartridge, the amount of a toner remaining in the toner cartridge or the amount of a toner remaining in the intermediate hopper is detected by a sensor. Depending upon the result of the detection, a notice is given to make a user aware of the necessity of toner cartridge replacement.
In the image forming apparatus disclosed in Japanese Unexamined Patent Publication JP-A 2005-84072, when a remaining amount detection sensor disposed within a toner hopper detects that the amount of toner accumulation within the toner hopper has been decreased to a specified level or below, then a toner bottle is rotated to effect toner replenishment for the toner hopper. When the result of the detection provided by the remaining amount detection sensor is found to stay the same (the amount of accumulation is found to be less than or equal to the specified level) even after the number of rotation of the toner bottle reached a specified rotational number or even after a lapse of specified rotational time, then the emptiness of the toner bottle is recognized and a request for toner bottle replacement is indicated.
In a case where a plurality of toner cartridges are provided, detection of a toner remaining amount is carried out for each of the toner cartridges on an individual basis. In this case, every time any one of the toner cartridges is emptied (the remaining toner amount has been decreased to a specified level or below), the operation of the apparatus is brought to a halt and a message of a request for toner cartridge replacement is indicated.
When it is detected that a toner cartridge for a black toner is emptied, the operation of the apparatus is brought to a halt and a message of a request for replacement of the black toner cartridge is indicated.
At that point of time, even if the remaining amount of a toner in a toner cartridge for a yellow toner is getting so small, there is given no indication of a message of request for replacement of the yellow toner cartridge. Therefore, the user replaces only the black toner cartridge with a new one in response to the request for replacement. If the replacement of the yellow toner cartridge becomes necessary immediately after the replacement of the black toner cartridge, the operation of the apparatus has to be brought to a halt once again to carry out a replacement procedure. This gives rise to a problem that the user is required to carry out toner replacement procedures many a time in a short period of time.